The present invention relates to rotating machinery such as a screw type compressor or supercharger. More specifically, the present invention is directed to an effective seal that is easy to manufacture using common manufacturing techniques and allows axial motion without constraint where an interface without steps is used.
Gaseous screw compressors of generally known configuration (FIG. 2) are considered flooded when the lubricant and gas streams mix within the compressor as shown in the flow schematic represented in FIG. 1. The mix is compressed to high pressure at the discharge end of the screws and exits the compressor. Lubricant and gas are then separated, and only the separated lubricant is reintroduced to bearings on the compressor screw shaft very near to where the mix was compressed to high pressure. The process is continuous, so a high-pressure mix is always present at the bearings. For lubricant to flow into a bearing, that bearing must, of course, be in a lower pressure region than the region where the mix was separated. This is conventionally accomplished by routing the bearing lubrication drain path to the low-pressure side of the compressor, adding a restrictor in the lubricant feed line, and most importantly introducing a shaft seal to block high pressure at the discharge end of the screws from directly flowing into the bearing and lubricant drain. Drained lubricant is reintroduced at the compressor inlet. Without a shaft seal, the high discharge pressure would have a direct path to the compressor inlet. This shaft seal is thus critical to compressor efficiency and lubrication system function.
Our invention is the discovery of a series of shapes or configurations that allows a tight seal between rotating components of different speeds to be achieved without the need for any contact. One advantage of our invention is that only one component surface needs to be smooth, thereby greatly simplifying machining operations and reducing costs. The mating surface of the present invention has a series of negative features of basic geometry, also further simplifying machining operations. The combination of smooth surface(s), when arranged parallel to the rotation axis, and mating negative features allows significant axial motion between the components without constraint while creating a highly effective seal that can be symmetrically shaped to create a seal from either direction. The effectiveness of this seal is not diminished when used in either a stepped configuration or a tapered configuration.